Proton implantation was found to reduce the free carrier density via 2 mechanisms; firstly by creating electron and hole traps, at around Ec-0.8eV and Ev+0.9eV, that led to compensation in both n-type and p-type material and, secondly, by leading to the formation of (AH)º complexes, where A was Mg, Ca, Zn, Be or Cd. The strong affinity of H for acceptors led to markedly different redistribution behaviours for implanted H+ in n-type and p-type material, due to chemical reactions which produced neutral complexes in the latter. The acceptors could be reactivated by annealing at above 600C, or by electron injection at 25 to 150C. This caused de-bonding of the (AH)º centres. Implanted H was also strongly attracted to regions of strain in heterostructure samples during annealing. This led to piling-up at epi-epi and epi-substrate interfaces. Infra-red spectroscopy showed that implanted H decorated VGa defects in the undoped or n-type nitride.

Effects of Hydrogen Implantation into GaN. S.J.Pearton, C.R.Abernathy, R.G.Wilson, J.M.Zavada, C.Y.Song, M.G.Weinstein, M.Stavola, J.Han, R.J.Shul: Nuclear Instruments and Methods in Physics Research B, 1999, 147[1-4], 171-4